I have traveled all over Europe and beyond, always with my camera, many time with rolls of Delta 3200, always had it X rayed, and never had a problem with fog or whatever. I really wonder whether these two pages of hysterical warnings here are based on practical experience or just propagated myths.

That was kind of why I was asking this question, to find some people with practical experience with delta 3200 and X-rays. My thoughts are to try my hardest not to get it stayed the. To not sweat it of it does.

I'm considering returning my film to bh and buying in London then risking the X-ray on the train to Paris then developing as I go. Though seems like a hassle.

Unfortunately the prices I seem to find in Paris don't seem ideal, anyone know a good retailer?

I think the prices are about the same. For example, Silverprint sells Delta 3200 in 120 size for 5.63 pounds, and in Paris Prophot sells it for 6.76 euros. According to the exchange rate, they're virtually the same price. Of course, it's more expensive than in the States, but then again, most things are.

As I understand it, the X-ray emissions are fixed, and the inspectors can only increase the gain of the sensor, so that is not an issue.
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True, and it is more accurate that they adjust various imaging options based on their x-ray 'capture'. But what I can assure you as a possibility (probability) is that they can put your film through the machine a second time... but without the lead bag the second time.

I bought my 120 b&w and color film in Italy, (Venice and Rome), had it developed there. MUCH less stress!!! You WILL have your film X-rayed at Heathrow-- coming and going, and the jerks at Heathrow are a major PITA,
they are obstinant and very annoying, self-important asses. Ask me how i really feel!!

Where did you develop your film in Rome and how fast was the turn around time?

I avoided Heathrow for about 15 years, then broke down and transited that airport in December 2012. Thank goodness I had upgraded my wife and I to business, which meant we only spent two hours getting through the morass of people. I mean no disrespect to the UK and its wonderful citizens, but I will again avoid Heathrow for another 15 years. FWIW, I found Munich to be a very efficient and friendly airport, unlike Frankfurt which seems to be on a never-ending refurb.